/Engine/Source/Runtime/Slate/Public/Framework/Docking/TabManager.h
Use this standalone RestoreSplitterContent when the output of its internal RestoreArea_Helper cannot be a nullptr.
void RestoreSplitterContent ( const [TSharedRef](API\Runtime\Core\Templates\TSharedRef)< [FSplitter](API\Runtime\Slate\Framework\Docking\FTabManager\FSplitter) > & SplitterNode, const [TSharedRef](API\Runtime\Core\Templates\TSharedRef)< class SDockingSplitter > & SplitterWidget, const [TSharedPtr](API\Runtime\Core\Templates\TSharedPtr)< [SWindow](API\Runtime\SlateCore\Widgets\SWindow) > & ParentWindow, FSidebarTabLists & OutSidebarTabs )